// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/display/util/display_util.h"

#include <stddef.h>

#include "base/logging.h"
#include "base/macros.h"

namespace ui {

namespace {

    // A list of bogus sizes in mm that should be ignored.
    // See crbug.com/136533. The first element maintains the minimum
    // size required to be valid size.
    const int kInvalidDisplaySizeList[][2] = {
        { 40, 30 },
        { 50, 40 },
        { 160, 90 },
        { 160, 100 },
    };

    // The DPI threshold to detect high density screen.
    // Higher DPI than this will use device_scale_factor=2.
    const unsigned int kHighDensityDPIThresholdSmall = 170;

    // The HiDPI threshold for large (usually external) monitors. Lower threshold
    // makes sense for large monitors, because such monitors should be located
    // farther from the user's face usually. See http://crbug.com/348279
    const unsigned int kHighDensityDPIThresholdLarge = 150;

    // The width threshold in mm for "large" monitors.
    const int kLargeDisplayWidthThresholdMM = 500;

    // 1 inch in mm.
    const float kInchInMm = 25.4f;

} // namespace

bool IsDisplaySizeBlackListed(const gfx::Size& physical_size)
{
    // Ignore if the reported display is smaller than minimum size.
    if (physical_size.width() <= kInvalidDisplaySizeList[0][0] || physical_size.height() <= kInvalidDisplaySizeList[0][1]) {
        VLOG(1) << "Smaller than minimum display size";
        return true;
    }
    for (size_t i = 1; i < arraysize(kInvalidDisplaySizeList); ++i) {
        const gfx::Size size(kInvalidDisplaySizeList[i][0],
            kInvalidDisplaySizeList[i][1]);
        if (physical_size == size) {
            VLOG(1) << "Black listed display size detected:" << size.ToString();
            return true;
        }
    }
    return false;
}

float GetScaleFactor(const gfx::Size& physical_size_in_mm,
    const gfx::Size& screen_size_in_pixels)
{
    if (IsDisplaySizeBlackListed(physical_size_in_mm))
        return 1.0f;

    const unsigned int dpi = static_cast<unsigned int>(
        kInchInMm * screen_size_in_pixels.width() / physical_size_in_mm.width());
    const unsigned int threshold = (physical_size_in_mm.width() >= kLargeDisplayWidthThresholdMM) ? kHighDensityDPIThresholdLarge : kHighDensityDPIThresholdSmall;
    return (dpi > threshold) ? 2.0f : 1.0f;
}

int64_t GenerateDisplayID(uint16_t manufacturer_id,
    uint32_t product_code_hash,
    uint8_t output_index)
{
    return ((static_cast<int64_t>(manufacturer_id) << 40) | (static_cast<int64_t>(product_code_hash) << 8) | output_index);
}

} // namespace ui
